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yE. MURPHY 2,853,683 v- HYBRIp JUNCTION Filed April so, 195s sept. 23,1958

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United States PatentOf 2,353,683 HYBRID JUNCTION Edward J. Murphy, Los Altos, Calif., assigner to Sperry d Corporation, a corporation of Delaware Application April 30, 1953, Serial No. 352,141

14 Claims. (Cl. S33-11) This invention relates to microwave transmission 'apparatus, and more particularly, is concerned with a folded type of hybrid junction. This invention lis related to the copending application Serial No. 352,244 filed April 30, 1953 in the name of P. Gene Smith and assigned to the This application vissued as Patent 2,792,551 on May 14, 1957.

As is well known to those skilledA in the art, the hybrid junction or so-called magic tee type of junction includes four wave guide arms which intersect in such a manner that two of the arms are collinear extensions of each other, and theA other two branch arms are at right angles to each other and to the collinear arms. Patent No. 2,445,895. This structure has balanced characteristics like those of a hybrid coil and is used for analagous purposes at the relatively high frequencies where wave guides find their principal applications.

As a result of the peculiar coniiguration of the hybrid junction in which the branch arms are mutually per` pendicular with each other and with the collinear arms, the use of the magic tee type junction frequently results in a ponderous and unhandy microwave transmission line layout. While such space-consuming wave guide circuits f may be tolerable in laboratory equipment, for example, use of the magic tee for this reason has proved troublesome in airborne radar systems where compactness is essential.

It is the general object of this inventionto avoid and overcome the foregoing and other diculties of and objections to the prior art practices by the provision of an improved wave guide hybrid junction.

Another object of this invention is to provide a hybrid junction in which the collinear arms are folded so as to be parallel to each other and substantially aligned with one of the branch arms whereby a much more compact z physical design is achieved.

These and other objects of the invention which will become apparent as the description proceeds are achieved by providing a hybrid junction in `which the -usual co1- linear arms are in effect folded back so as to be posi- 2 tioned in parallel relationship to each other with a common broad wall in the form of a `septumseparating the" show'internal details of a hybrid junction without the' coupling flanges or 'attached wave guide lines;

Fig. 2 is a sectional view of the junction shown in Fig, 1 and showing coupling flanges ou the branch arms;

, 2,853,683 Patented Sept. 23, 195s ICC Fig. 3 is a plan view, partially -in section, ofthe hybrid junction of Fig. 2;

Fig. 4 is a sectional view of a modied form of junction junction which correspond in function to the usual 'collinear arms of the standard form of magic tee. The numeral 14 indicates generally one of the branch arms of the folded hybrid junction which corresponds in function to the series arm of the standard magic tee while the numeral 16 indicates generally the other branch arm of the present hybrid junction which corresponds inv function to the shunt arm of the standard magic tee.'k

The arms 10, 12, 14, and 16 will hereinafter be-referred to in terms of their equivalentk functions in the conventional type of magic tee structure'.

In accordance with the embodiment of the invention illustrated in Figs. l through 3, the numeral 18 indicates generally a section of hollow pipe having a section 19 which is substantially square in cross section. At one end thereof, the hollow pipe 18 is reduced in one crosssectional dimension to form a rectangular section 20, the tapered section of the pipe 18 joining the square and rectangular sections being indicated at 22. A second hollow pipe, indicated generally at 23, includes a rectangular wave guide 24`that is joined at one end to the top wall of the first pipe 18 by means of a tapered transition section 26, the iirst pipe-18 and second pipe 23 extending at right angles to each other. The second pipe is joined to the rst pipe in the region of the tapered transition section 22.

A septum, indicated generallylat 30, extends between the top and bottom walls of the iirst pipe 18 in the square section 19 dividing it into two adjacent rectangular wave guides which form the two collinear arms 10 and 12 of the hybrid junction. The septum 30 extends into the region of the junction and terminates in an edge 32 which lies substantially along the longitudinal axis of the second pipe 23. A portion 36 of the septum 30 extends up into the shunt arm 16 along the edge 32 and terminates in -a tapered edge 38 which provides a gradual transition for energy coupled from the second pipe 23 into the lirst pipe 18, thereby reducing reection of energy back along the shunt arm 16. A flange 44 may be provided for coupling a wave guide transmission line to the shunt arm 16 of the hybrid junction. Likewise, a'ange `45 may rbe provided for coupling a wave guide transmission line-to the series arm 14 of the hybrid junction. l

To function as a magic tee, the junction must provide complete isolation between the branch arms 14 and 16,v

that is, no energy must be coupled directly from one' branch larm into the other. Likewise, there must be isolation between the collinear arms 10 and 12. To ac The match between the series arm 14 and the col# linear arms 10 and 12 is provided by the tapered section 22, the section 22 providing a gradual transition between the rectangular section 20 forming the ser-ies arm 14,

and the collinear arms 10 and 12. Since the electricelly of the dominant mode in the rectangular section 20 is perpendicular to the septum 30, the latter causes negligible reilection at the edge 32. Any mismatch caused by rheepening at the junction With the second pipeZcan.,

. 3 be minimized by proper tapering of the YwallshofV `the section '22 and by proper positioning of the junction along the tapered section 22.

The portion 3 6ofntheseptum 30'extendingfupHinto the second pipe 23 effects coupling of energy transmitted therein in the dominant mode into'the collinear. arms il@ and 12 by distorting the fieldconfguration- ,along the ta- Y pered edge `3S in the manner indicatedV by the arrows in Figs. l and 3. It will be seen that the distortedfield has components perpendicular tothe face of the `septum Sti which couple energy in thehdominant mode into the arms and 12 as indicated by the dotted arrows of Fig. 3; Due to the symmetry of the'field produced, these perpendicular components oppose each other in the brancharm 14, so that no energyfrom -the arm i6 is propagated back along the' series arm 14. Energy in the shunt arm 16 having electric field components parallel to the septum tends to be propagated transversely across the first pipe 18 along the edge32 of the septum, but the series arm 14 and collinear arms lo i and 12 of the hybrid junction are below cut-off for the mode which can be set up by these components, so that no energy is coupled between the series and shunt arms.

Referring to the form ofthe invention illustrated in Figs. 4 and 5, a modified forni of the folded hybrid junction above described is shown in which-the shunt arm 16 is provided by a coaxial transmission line indicated at 48. The outerV conductor of the coaxial line 48 is joined at one end to the wall of the tapered section 22;

the inner conductor 52 of the coaxial line 48 extends into the interior of the hollow pipe 18. In the modified form, the septum 30 terminates in an edge 54 which extends between the top andV bottom walls of the pipe 18 at an acute angle therewith. The inner conductor 52 of the coaxial line 50 terminates along the tapered edge 54 of the septum 30, the position of the edge 54 along the hollow pipe 18 being'such that the conductor 52 extends substantially across the hollow pipe 1S, as is apparent from the drawing.

Although the shunt arm 16 in the modified form of Figs. 4 and 5 is coaxial, the operation is substantially the same as the hollow wave guidev form of Figs. 1-3.

Energy in the series arm V14 is divided between the two collinear arms 10-and 12 by the septum 3f), the energy in the two collinear arms being in phase. Energy in the coaxial linehof the shunt arrn has components of the electric field which are perpendicular to the septum 3f) and thereby couple energy into' each of the two collinear arms, the energy being in phase opposition in the two This phase opposition .results in cancollinear arms. collation of energy coupled'back into the series arm 14. Components of the electric field of energy in the coaxial line 48 which are parallel to the septum 30 can onlyset up a mode ofA propagation in the pipe 13 for which the rectangular sectio'n20'V is below cut-off. Thus,.substan tiallyv complete isolationA between the coaxial shunt arm 16 and the series arm 14 is effected.V

Fror'n the abovedescription it will be recognized that the various objects of the invention have been achieved by the provision of a hybrid junction which is much more compa'ctthan the conventionalnragic tee and yet gives equivalent performance. Actually the junction can be usedl in a space no wider than the width dimensions necessary for a wave guide transmission line.

i Since many changes could be made in the above construction and `many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter containedy in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not Vinl a limiting sense.

What is claimed is:

1. A folded hybrid junction comprising a first hollow pipe having a rectangular section,` a square section, and a* tapered section joining the square and rectangular sections, the first pipe sections being aligned along a common longitudinal axis, a second hollow rectangular pipe joined to the first pipe in the region of the tapered section thereof, the longitudinal axes of the first and second pipes intersecting at right angles, and a septum lying in the plane defined by the intersecting axes and extending the entire distance between opposite walls of the square section of the first pipe for dividing the square section into two parallel wave guides, the septum terminating in the tapered section of the first pipe in an edge extending parallel to the longitudinal axis of the second pipe, a portion of the septum extending into the second pipe -along the wall of the second pipe nearest the square section of first v pipe and having an edge spaced from the opposite wall of the second pipe, said lastnamcd edge being an extension of said terminating edge of the septum, said portion being tapered at the end thereof projecting farthestinto `the second pipe.'

2. A folded hybrid junction comprising a first hollow pipe having a rectangular section, a squaresection, and a tapered section joining the square and rectangular sections, .the first pipe sections beinglaligned alonga common longitudinal axis, a second hollow rectangular pipe joined to the first pipe in the region of the tapered section thereof, the longitudinal axes of the first and second pipes intersecting at right angles, and a septuml lying in the plane defined by the intersecting axes andA extending the entire distance between oppositewalls of the square section of the firstpipe for dividing the square section into two parallel wave guides, the septum extending' partially into the tapered section of the first pipe and 'extending partially into the second pipe, the septum terminating in an edge extending substantially along the longitudinal axis' of the second pipe from the wall of the first pipe opposite the junction with the second pipe to a point within the second pipe, the edge of the septum tapering off from said point to the adjoining wall of the second pipe.

3. A folded hybrid junction comprising a first hollow pipe having a rectangular section, a square section, and a tapered section joining the square and rectangular sections, the first pipe sections being aligned along a common longitudinal axis, a second hollow rectangular pipe joined to the first pipe in the region of the tapered section thereof, the longitudinal axes of the first and second pipes intersecting at right angles, and a septum lying in the plane defined by the intersecting axes and extending the entire distance between opposite walls of the square section of the first pipe for dividing the square section into two parallel wave guides, the septum terminating in the tapered section of the first pipe in an edge extending parallel to the longitudinal axis of the second pipe, a portion of the septum extending into the second pipe along the wall of the second pipe nearestk the square sectiony of first pipe and having an edge spaced from the opposite wall of the second pipe, said last-named edge being an extension of said terminating edge of the septum.V

4. A folded hybrid junction comprising a first hollow pipe having a rectangular section, a square section, and a tapered sectionjoining the square and rectangular sections, the first pipe sections'being aligned along a common longitudinal axis, a second hollow rectangular pipe joined to the first pipe in the region of the tapered section thereof, the longitudinal axes of the first and second pipes intersecting at right angles, and a septum lying in the plane defined by the intersecting axes and extending the entire distance between opposite walls of the square section of the first pipe for dividing the square section into two parallel wave guides, the septum terminating in the tapered section of the first pipe in an edge extending parallel tothe longitudinal axis ofthe second pipe, a portion of the septum extending into the second pipe along the wall of the second pipe nearest the square section of first pipe Aand havingy an ,edge spaced from the opposite wall of the second pipe.

5. A folded hybrid junction comprising a first hollow pipe having a rectangular section, a square section, and a tapered section joining the square and rectangular sections, the first pipe sections being aligned along a common longitudinal axis, a second hollow rectangular the square section ofthe first pipe for dividing the square,

section into two parallel wave guides, the septum terminating in the tapered section of the first pipe with a portion of the septum extending into the second pipe' along the wall of the second pipe nearest the square section of first pipe and having an edge spaced from the opposite wall of the second pipe.

6. A folded hybrid junction comprising a first hollow pipe having a rectangular section, a square section, and a tapered section joining the square and rectangular sections, the first pipe sections being aligned along a common longitudinal axis, a second hollow rectangular pipe joined to the first pipe in the regionof the tapered section thereof, the longitudinal axes of the first and second pipes intersecting at right angles, and a septum lying in the plane defined by the intersecting axes and extending the entire distance between opposite walls of the square section of the first pipe for dividing the square section into two parallel wave guides, the septum terminating in the tapered section of the first pipe with a portion of the septum extending into the second pipe.

7. A folded hybrid junction comprising a first hollow pipe, a second hollowpipe joined at one end to one wall of the first pipe to form a T-junction, the longitudinal axes of the first and second pipes intersecting each other, and a septum lying in the plane dened by the intersecting axes and being positioned in the first pipe substantially to one side of the junction with the second pipe, the septum terminating in an edge lying substantially along the longitudinal axis of the second pipe, a portion of the septum extending into the second pipe,

8. A hybrid junction comprising parallel rectangular sections of wave guide having a thin common broad wall therebetween, a rectangular wave guide section substantially aligned with said parallel sections, the broad walls of the rectangular section lying in planes parallel to said common wall, a tapered wave guide section joining said parallel sections to said rectangular section at their respective ends, said common broad wall' extending partially into the tapered wave guide section, and a branch wave guide coupled at one end into the tapered wave guide section through a wall in the tapered section that is perpendicular to said common wall.

9. A hybrid junction as set forth in claim 8 wherein the branch wave guide is a coaxial line.

10. A hybrid junction as set forth in claim 9 wherein said common wall terminates in an edge extending at an acute angle between opposite walls of the tapered wave guide section, the inner conductor of the coaxial branch wave guide extending into the tapered wave guide section and terminating at saidedge of the common wall'.

11. A hybrid junction comprising parallel rectangular sections of wave guide having a thin common wall therebetween, a rectangular wave guide section substantially aligned with said parallel sections, the two opposite walls of said rectangular wave guide section corresponding to said common wall lying in planes parallel to said common wall, a tapered wave guide section joining said parallel sections to said rectangular section at their respective ends,` said common wall extending partially into the tapered wave guide section, and a branch wave guide coupled at one end into the tapered wave guide section through a wall in the tapered section that is perpendicular to said common wall. v

12. A hybrid junction comprising parallel rectangular sections of wave guide having a thin septum serving as a common broad wall therebetween, a rectangular wave guide section substantially aligned with said parallel sections, the broad walls of the rectangular section lying in planes parallel to said common wall, a tapered wave guide section joining said parallel sections 'to said rectangular section at their respective ends, and a branch wave guide coupled at one end into the tapered wave guide section through a wall in the tapered section that is perpendicular to said common broad wall, said common broad wallcxtending into the tapered wave guide section and terminating at least partially within the projected area of said branch wave guide and being in physical and electrical contact with a portion of the branch wave guide.

13. A hybrid junction as set forth in claim 12 wherein the branch wave guide is a coaxial line.

14. A hybrid junction as set forth in claim 13 wherein said common wall terminates in an edge extending at an acute angle between opposite walls of the tapered wave guide section, the inner conductor of the coaxial branch wave guide extending into the tapered wave guide section and terminating one said edge of the common wall.

References Cited in the file of this patent UNITED STATES PATENTS 2,445,895 Tyrrell July 27, 1948 2,575,804 Friis Nov. 20, 1951 2,584,162 Sensiper Feb. 5, 1952 2,593,120 Dicke Apr. 15, 1952 2,643,295 Lippmann June 23, 1953 2,691,731 Miller Oct. 12, 1954 2,764,740 Pratt Sept. 25, 1956 

